Comments

I use a lot of lithium tool batteries. It is a much better technology in many ways. But the prices for lithium solar batteries are still iffy in my estimation. My vote would be for lead acid for the next ~5 years. Then see what lithium is offering.

Unless, perhaps, you can get a great deal on a used lithium automobile battery. May be worth checking into.

Lithium (of which there are multiple types with distinct characteristics), solves some problems, but creates others. Some include inability to charge in cold temps, greater risk of fire, difficulty in using voltage as a SOC indicator, and cost.

These can be overcome with some chemistries in some applications, but for my off-grid application, like softdown, I think I'll wait a bit for costs to come down.

Cold is an issue and so is heat. More so than LA. They like the temperatures humans do and do not like a shed out in the tundra/desert.I think the cost is not going to come down.I also think if you do the math, they could outlive you guys. The Soc accuracy is one of the main attributes of Lithium chemistries and their integrated BMS.Incredibly accurate Soc !

Lithium batteries are still a bit "bleeding edge". If they do not get you something, probably waiting 5 years is not a bad idea. Li Ion batteries generally have an integrated battery management system--That should feed back to the inverter, solar charger, etc. -- That is still not a common configuration at this time.

I've been using a 12 kWh prismatic LiFePO4 bank for over 2 years now and it is 99% efficient and very reliable. It is installed in an air conditioned space, temps vary from 60 to 78 degrees over the year. I cycle it down to 28% but most days during the summer, the bank doesn't reach 100% due to poor solar weather and because I keep a load on it all day with the A/C running. Honestly it pretty much works like an appliance. It also works well with Outback's Grid Zero mode, sort of set it and forget it. But I micro manage it to get maximum production. Like @Dave said, SOC is very accurate if using a good battery monitor, for me that's Midnite's Wizbang Jr. wired to a Classic 150. This bank is probably cycling at about 60% which should go for about 4000 cycles if usage doesn't change. LFP is expensive, my bank was 3300 dollars. A similar bank today would be about 4000 dollars, consisting of 16 or 17 3.2 volt 200AH prismatic cells in series.

I have a friend that purchased a 7 kWh lithium battery for around $7000 CAD and ended up not needing it. Might be a good chance to purchase at a discount and experiment with it. Being dead in the water when its below freezing does not sound fun and I am not too comfortable with lithium to close to where the family resides. I am considering installing a Mitsibishi or Fujitsu heat pump to climate control the framed, and insulated sea-cans but even then in very cold climates (below -25 C)the heat pumps are not feasible. Might have to cut my teeth on the batteries I have now and go from there.

If you guys had purchased 12 - 12V batteries not knowing any better would you back out and buy something more suitable for off-grid or would you carry on towards the iceberg. Not excited about 3 strings.....

Personally, if I already had the three strings of 12v batteries, I'd do the best I can with what I have. If you wire them properly, and monitor for/remediate potential problems by checking SG regularly etc, you can do fine. Ideally, a single string is best/easiest, but you can make multiple strings work too. It just takes a bit more work and vigilance.

If it was me and I knew which Li chemistry I would ask make model, serial number, type /make of BMS ,etc... the good thing about most Li chemistries is that they can sit for a long time with no degradation as opposed to FLA etc...

I did do a couple weeks of research on FLA and my 12 V batteries in particular and have charged them regularly and equalize them in separate strings as they sit waiting to be put into service. I think the reason my supplier bought the 12 V batteries was simply price point I am assuming because 12 V batteries are probably more mass produced?

Those batteries are approved for use with Schnider Xanbus charge controllers and inverter chargers, which I believe is what you have, or are considering. @Dave Angelini was, I believe, testing their compatability for Schneider, perhaps the best person with hands on experience to offer an opinion, that I'm aware of, he mentioned cost was ~$ 1000 per Kw. As far as lithium batteries are concerned, I often wonder if it's the fear of fire associated with some chemistries which paints them all with the same brush, all I'm definitely not an expert, but from what I've read and understand is that LiPo4 are safe if properly used with an applicable BMS.

As Mcgivor said or the update is that is all I use for my new clients who have reasonable temperatures and Schneider electronics. Outback soon will interface directly with the AES.

It is a common configuration at this time Bill because I would not use anything that does not interface the BMS, battery, and Soc/temp directly from the battery manufacturer into the system over Schneider insight or soon Outback optics. The reason I do not think they will comedown is simply the cost of the materials in an LFP battery. They are going up lately. The BMS is pretty simple and electronics do tend to come down. I definitely would not buy a lead acid if i knew that this was for the long haul and that I could keep them at temperatures that are pretty well spelled out in the warranty. Partial cycling is what people forget to add when they cost an LFP battery BTW.

Having accurate Soc, Not worrying about being full on a regular basis, = Priceless offgrid if you live there full time!

I really respect what Rick has done but I could never use that system for a client and maybe that is what BB is referring to.

I just looked, at close to 2 years I am still at 99% state of life from my BMS. A bit of math and at the rate we cycle, about 34 years left. I do live within an hour of Costco if the math is wrong My clients really like this battery, I mean really like it! Cheers!

As Mcgivor said or the update is that is all I use for my new clients who have reasonable temperatures and Schneider electronics. Outback soon will interface directly with the AES.

It is a common configuration at this time Bill because I would not use anything that does not interface the BMS, battery, and Soc/temp directly from the battery manufacturer into the system over Schneider insight or soon Outback optics. The reason I do not think they will comedown is simply the cost of the materials in an LFP battery. They are going up lately. The BMS is pretty simple and electronics do tend to come down. I definitely would not buy a lead acid if i knew that this was for the long haul and that I could keep them at temperatures that are pretty well spelled out in the warranty. Partial cycling is what people forget to add when they cost an LFP battery BTW.

Having accurate Soc, Not worrying about being full on a regular basis, = Priceless offgrid if you live there full time!

I really respect what Rick has done but I could never use that system for a client and maybe that is what BB is referring to.

I just looked, at close to 2 years I am still at 99% state of life from my BMS. A bit of math and at the rate we cycle, about 34 years left. I do live within an hour of Costco if the math is wrong My clients really like this battery, I mean really like it! Cheers!

I agree, @Dave, it's not a system for clients. But for someone who manages their own system and understands LFP balancing and charging characteristics, it works well and the price is hard to beat.

Great discussion. Dave, so the 48 V Discover AES Lithium is "THE" battery, at the present, for Schneider equip hey? And yes that is what I have now, everything Schneider. XW+ 6848, 2 - MPPT 60 150's, SCP, Battery monitor, Com box, AGS.

Also, would 4680 watts of PV (STC) be appropriate with that 7 kw Discover Lithium battery or severely undersized? With the potential to push 130 A in to the battery, although not necessary and not sure why you would want to too due to excess heat, what is an appropriate sized back up generator. Obviously not a 130 A output generator (that'd be huge and $$$) or do you increase PV for your AES clients? I like this little guy so far:

FLA's seem to be an old, simple design which can handle the cold. If you can climate control the area the Lithium will go then it mat be a great solution in the near future. Power wall 2 self regulates temp (though at a consumption of stored energy I am sure).

All battery chemistrys have their pros and cons, choose the ones interested in, make a column for each, list all criteria, in a spreadsheet format, high temperature performance, low temperature performance, self discharge, efficiency, life span, depth of discharge ability, weight, ease of maintenance etcetera, etcetera, then tick the boxes. That's what I did and lifepo4 came out on top for my application so that's the road I'm going down, lots to learn no doubt, but being the proverbial fly on the wall reading others posts, it would seem individual prysmatic cells is the cost effective option. The price is competitive with LA considering cycle count, my cost for 450Ah LA was $1187, 200Ah LiFePO4 $1232 at 24V nominal, plus BMS, import tax and shipping, still working on that. The first system will be a learning system, not the primary which will actually be smaller, thinking around 100Ah, 24V nominal, going to be interesting.

> @ligwyd said:
Power wall 2 self regulates temp (though at a consumption of stored energy I am sure).
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My understanding is none of the lithium chemistries should be charged below freezing. Not sure how PW or others do it, but I would design it so available incoming R.E. power is used first to warm the bank, and charging enabled only when bank reaches a min temp. Using stored energy would run the risk of of a cycle of heating and cool-down with intermittent sun and overdischarge, and strikes me as a bad idea.

Winter time insulation panels, and DC heat pads , so little internal resistance that there is little self heating with solar charge rates. None of the Li formulas that I know of, can charge below frost.

I don't think that one needs to do this Mike. Design for a proper battery room that is a conditioned space. Not that hard to do unless one is leaving the home unattended. That is the real challenge to me and some of my clients in places like Alaska and Canada.

It takes very little energy to heat a well insulated battery box. So you could wire a single panel directly to a small, thermostatically controller heater. This resolves the chicken/egg problem if an unattended main bank gets drained and too cold.